The pagination works similar way as in XF2 profile comments.
There is added extra top row, on the left side you can see the total number of comments in the reply. And on the right side is the link to get to the rest of the comments.
By default, last 3 comments are always visible. In the settings you can set how many comments you want to keep visible. However, unread comments are always displayed all on a 1st visit.
In the first option you set the number of latest comments you want to see under the reply on a page load. Setting it to 0 will load all comments.
With the second option "View previous comments", you can set the number of comments loaded when "View Previous comments..."link is clicked. Setting it to 0 will load all comments.
- Option in the admin area to count also comments to the total message count. By default unchecked. This option will include also the forum comments under replies in the total messages count. And also the user's total message count will be updated. NOTE: You need to rebuild the threads and user caches.
NOTEIf a reply becomes so popular that gathers more than 40-80 comments, I think that reply might deserve to be moved to own thread. IMHO.
NOTE Comments (the same way as profile comments, media comments) by default don't count to the total message count. However, if you want them to count, there is an option in the admin area to allow it: "Count forum comments towards the total messages count.".
NOTE Unread comments are always displayed all on a 1st visit.